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CalSol recently visited SunPower at their Richmond office on November 5, 2014. We displayed our newest racing vehicle, Zephyr, and discussed our progress and future plans and projects. We also took Zephyr for a spin in their parking lot and shared ideas with some of their engineers who helped us with our solar array.

CalSol incorporates SunPower High-Efficiency Gen-E solar cells in Zephyr. SunPower’s innovative solar cells have been critical to unleashing the full performance of our vehicles. CalSol is also incredibly grateful for SunPower’s continued generosity and support throughout the years by providing us with the resources and facilities necessary to create our solar array. Our success would not have been possible without you!

Starlink Co. has yet again provided us with stickers and decals for Zephyr, free of charge. Starlink is a leader in digital printing, and the kind folks at Starlink even expedited our decals order so we can have them on the car before FSGP/ASC! Thank you very much for your support!

The beautiful decals adorning Zephyr’s top shell

The CalSol & Cal decals also made it on Polytechnique Montreal’s Esteban!

Saturday July 19th was CalSol’s first and last day participating in the Formula Sun Grand Prix 2014 at the Circuit of the Americas. CalSol successfully got Zephyr on the track on Saturday morning. We were able to get a few laps around the track but soon discovered an electrical problem that caused the car to turn itself off after exceeding speeds around 30mph. To provide some context, it was necessary for Zephyr to reliably drive with a speed upwards of 60mph in order for us to take Zephyr on public roads. On the Circuit of the Americas track, one of the very first hurdles was getting past a steep hill before going around the first corner. After a few laps around the track, Zephyr started to cut off its power while climbing the hill.

Zephyr at the starting line of FSGP

We discovered that the electrical current limit of one of our systems was set too low, thus triggering a safety feature to shut down the car. This is an anomaly, as we have been able to take the car to speeds upwards of 50mph. We examined every connector, board, wire, and piece of software that we could get our hands on. We were at a constant hustle to get the car running on the track again—but each time it would stall after ten seconds of acceleration. Members frantically ran to and fro along the track with tools, computers, and debuggers.

This went on for six hours. Unfortunately, by the end of the day we had only completed five laps out of the required forty-eight. Though ASC can grant provisional qualification to teams that have a high potential, CalSol decided to withdraw from the race simply because racing a car with an unreliable electrical system on public highways posed a safety risk for the team.

We are very disappointed. We had come out to Texas to race to Minnesota and our FSGP/ASC2014 experience was cut short.

Without a doubt, forfeiting ASC2014 was one of the team’s lowest and the most humbling moments. We learned that the importance of extensive testing wasn’t just some rookie comment, but rather it was an absolute necessity for any team who wants to ensure a reliable vehicle. We experienced first-hand what it meant to push ourselves even when we thought we could not be pushed any further. And the most encouraging part is, we got to interact with the kind and intelligent solar car community who worked across team affiliations to get every car up and running.

In ASC 2012, CalSol reached a respectable 4th place finish on a simple but well-tested vehicle. After ASC 2012, CalSol went great lengths to build a solar vehicle with the most efficient aerodynamics and solar cells, lightest body and chassis, and the most advanced manufacturing techniques that the team had ever undertaken. Despite the measures taken to create the most advanced solar car, we fell short in producing a reliable vehicle.

Like every car, Zephyr succeeded in some aspects and failed in others.

Before packing up, there was one more thing we were able to do in order to help the solar car community. Polytechnique Montréal turned sharply on a tight corner on the track and snapped one of their car’s two Mitsuba motors. The team ingeniously found a way to power the car with a single motor in mere hours, and conditionally qualified for ASC2014. However, being short one motor without a spare was not a comfortable situation for the Montréal team. Since CalSol’s Zephyr uses the same equipment, we let Montréal borrow two Mitsuba motors for the race.

In 2003, CalSol had motor issues and ended up racing with University of Kentucky’s motor. This week we were able to pay that kindness forward. I like to call it solar car karma. Even though we will not be able to race, we are still honored to participate in such an amazing community. We hope that our competitors are able to reach their fullest potential.

With a great deal of dedication, perseverance, and solar car karma, we are making great progress in solar car innovation. We are using this experience as a stepping-stone for accelerated progress with Zephyr. We’ve identified key issues with over-eager safety systems and are developing a better testing strategy. The best days of this car have yet to be seen, and we are excited to see where we go next.

Min Ju Lee

CalSol team lead

CalSol 2014 team photo

Thank you GM for providing us with two Yukons for the race! While Zephyr will not make the trip up to Minnesota, several team members will travel with other teams up north to partake in the ASC 2014 racing experience.

The electrical team has been making good headway lately, with new, experienced, and alumni members all working to finish the assembly, testing, and troubleshooting of Zephyr’s electrical system.

The HCI (Human Control Interface) sub-systems are able to communicate among themselves over the CAN bus, which stands for Controller Area Network and allows for communication without a central computer. These sub-systems include the dashboard, accelerator and brake, steering wheel and side panel, and the two motor controller controller (which controls the motor controller, and is dubbed the MC^2). The controllers are working, and the motors are able to spin.

Regarding the solar cells, the solar array is coming together, with the team ready to finish placing the cells. The MPPT’s (Maximum Power Point Trackers, which keep the solar array at an optimal power output by manipulating on the I-V curve) are able to communicate over CAN as well.

Additionally, the two power hubs (which distribute power to the various electrical systems, which need to be kept on lines of separate voltages) are ready, and the BMS (Battery Management System) seems to be operational. All the electrical boards have been soldered, populated with components, and tested. The battery box has been built, and the fuses, connectors, and peripherals are being mounted.

The HCI system, including the LCD readout for the driver

The little nickel strip on the bottom of the module with the hole punched out is used to help measure voltage across the battery banks

Careful alignment of the solar array is required, since the indentations on the carbon fiber shell allow for little tolerance

We couldn’t have done this without the financial and technical support of our sponsors:

Advanced Circuits, for producing many of Zephyr’s PCB’s!

Bay Area Circuits, also for producing many of Zephyr’s PCB’s!

LEMO, for donating connectors!

Phoenix Contact, also for donating connectors!

Linear Technology, for giving LT boards and chips, providing monetary donations, as well as technical support and guidance!

With the Formula Sun Grand Prix / American Solar Challenge 2014 approaching in just a month, CalSol is in the process of organizing a list of generous friends and company sponsors who made it possible for us to engineer Zephyr and to enter in the SunRayce. In particular, the team decided to give a shout-out to our top three sponsors for this race. This shout-out to SunPower is dear to me because it’s what got me so hooked onto the team and also what led me to become the engineer that I am today.

Team members preparing for solar cell caulking.

SunPower Corporation is based in San Jose, Calif, and is America’s premier high-efficiency silicon solar cell designer & manufacturer. Almost all competitive teams participating in the American Solar Challenge use SunPower cells because not only are they efficient, they are also incredibly reliable. CalSol has been using SunPower cells dating as early as the late 90s, but we had never established a connection with the company until 2013.

With CalSol encapsulating our own solar cells for the first time this build season, we needed a lot of help. We talked to awesome local and corporate companies such as D2 Solar and Dunmore– the kind engineers from D2 solar and Dunmore gave us many samples to test and generously donated their time to troubleshoot our problems. We learned a lot, but we were far from being able to produce perfectly encapsulated panels.

By half-luck and half-coincidence, I got in contact with SunPower’s senior manager in business development. She is also a Cal grad and was intrigued by our project– and from there, the solar team’s progress took off quickly. We received bare SunPower solar cells, as well as invaluable engineering support from SunPower engineers. It’s been more than a year since SunPower and CalSol has been working closely together– and for over a year, the CalSol members have had the privilege of learning about the solar industry first-hand with the leading solar company in the world. And more importantly, we’ve had so much fun doing engineering.

Chatting up with SunPower’s CEO Tom Werner at 2013 All-Hands meeting

Impulse, the team, and SunPower’s executive officers at the Richmond, Calif. facility.

Solar cell encapsulation @ the San Jose HQ

The team is recognizing SunPower as one of our top three sponsors for Zephyr / ASC 2014. SunPower has not only provided CalSol with generous in-kind donation, but perhaps more importantly, invaluable engineering and moral support to the team. We know that the people at SunPower are busy individuals, and we cannot thank you enough for taking your time to help us with everything solar-related for Zephyr!

It’s been a while since our last blog update, but the intrepid CalSol crew has definitely been busy. Both Zephyr’s mechanical and electrical systems are nearing completion, and with all the work being put into making this our greatest vehicle yet, we’ve got plenty to report with new updates!

We would like to thank Vicor Corporation for their generous donation of the DC/DC converter and its appropriate mounting and connection accessories, as well as the assistance of their applications engineers in selecting the components! But first, what does a DC/DC converter do? (more…)